Stralian Hearing Annual Report 2003–04 - Australian Hearing

National Acoustic
Laboratories
“A critical source
of information in
hearing and noise
in Australia and
overseas.”
Testing the reception of sound within the
brain, using scalp electrodes, means hearing
aid effectiveness can be assessed in infants.
Over its 57-year history, the National Acoustic
Laboratories’ (NAL) research into hearing and noise
has improved the ways in which people with hearing
loss can be helped. NAL continues to contribute to
global research in acoustics, audiology, hearing aid
development and hearing loss prevention. Research
scientists present their work at Australian and
international conferences and publish work in
international journals and on the NAL website
(www.nal.gov.au). NAL’s audiological procedures are
widely recognised and adopted worldwide.
NAL’s acoustic test facilities in Chatswood include a
range of special-purpose rooms that are used for
acoustical research, testing and measurement
covering the full range of human hearing and
extending into infrasonics. These facilities are also
used to provide acoustical testing services for private
industry and government.
Infants’ hearing aids
In the past year, NAL has made significant progress on
a world-first study entitled Cortical Potentials which
investigates the brain wave activity associated with
sound. The aim of this study was to create technology
to evaluate the effectiveness of infants’ hearing aids.
Electrodes attached to the scalps of infants with
normal hearing indicated that when the babies
received different speech sounds, correspondingly
different patterns of electrical activity emerged from
the auditory cortex area of the brain. A similar result
occurred for many hearing-impaired infants wearing an
appropriately adjusted hearing aid. When these infants did
not have hearing aids, or had hearing aids with insufficient
amplification, no such patterns occurred.
This new technology is becoming increasingly relevant and
necessary now that NSW has introduced universal newborn
screening for hearing loss. More hearing-impaired babies, as
young as one month old, are now being fitted with hearing aids,
and the research is expected to lead to an objective method to
evaluate the appropriateness of the hearing aid fitting.
Detecting differences
NAL researchers have developed an automated statistically-based method to
detect differences in brainwave patterns in infants in response to sound. This
testing technique should be available commercially in a couple of years. The study
results have been presented at Australian and international conferences.
NAL research
The high international prominence of procedures developed by NAL became
evident during the year in two independent reviews.
• A survey published in the Hearing Journal in the USA in October 2003, cited the
NAL-Non linear 1 (NAL-NL1) prescription formulae as the most-used procedure
for prescribing non-linear hearing aids in the USA, while the NAL-RP formula
(for linear hearing aids) was the second most-used procedure.
• A survey published in Hearing Review in the USA in June 2003, showed that
the Client Oriented Scale of Improvement (COSI) procedure developed jointly
by NAL and Australian Hearing clinicians was the most-used procedure for
evaluating the outcomes of rehabilitation.
Three research studies completed during the year were:
• A study on Personal Stereo Noise Exposure found that one in four people
surveyed listened at volumes and for times that were equivalent to listening
at 85 dBA or higher for eight hours per day, placing them at risk of damaged
hearing.
• A study into the link between auditory processing disorders and reading ability
showed that children who were poor readers were less able to process sounds
within their auditory system than those who read well. The children studied
were between eight and 12 years old.
“More hearingimpaired
babies,
as young as one
month, are now
being fitted with
hearing aids.”
32 AUSTRALIAN HEARING ANNUAL REPORT 2003–04 NATIONAL ACOUSTIC LABORATORIES 33